Commodore VIC-20 - Subroutine Statements

140 POKE C - L , 8
150 NEXT
The screen color is white, the border color is cyan, the
character color is black, and the auxiliary color is light cyan.
You're not really putting color codes in the space for screen,
border, and auxiliary color; you're putting references to the
registers associated with those colors. This conserves memory,
since 2 bits can be used to pick 16 colors (screen and auxiliary) or 8
colors (character and border). This also makes some neat tricks
possible. Simply changing one of the indirect registers will change
every dot drawn in that color. So everything drawn in the screen,
border, or auxiliary color can be changed on the whole screen
instantly. Here is an example using the auxiliary color:
100 PRINT CHRS(147) CHRS(18);
110 POKE 646 , 8 ,
115 FOR L = 1 TO 22 : PRINT CHR$(32); : NEXT
120 POKE 646 , 6
130 PRINT "HIT A KEY"
140 GET AS: IF AS ="" THEN 140
150 X = INT (RND (1) "18)
160 POKE 36878 , X * 16
170 GOTO 140 |
There is a memory location in the VIC that is especially useful
with multi-color mode. Location 646 is the color that is currently
being PRINTed. When a color control key is pressed this location is
changed to the new color code- By POKEing this location, the
characters to PRINT can be changed to any color, including
multi-color characters. For example, type this command:
POKE 646.10
The word READY and anything else you type will be displayed in
multi-color mode. Any color control will set you back to regular text.
SUPEREXPANDER CARTRIDGE '
There is a cartridge program called the VIC SUPER EX
PANDER. This cartridge is programmed with many special
functions, including a graphics package. This allows drawing of
lines, dots, and circles, coloring in of areas on the screen, and full
control over graphic modes. For programs in BASIC, it will be
considerably easier to use graphics with the SUPER EXPANDER
than by use of cumbersome pokes. The SUPER EXPANDER also
includes 3K of extra RAM to give you enough room to do any
high-resolution operation.
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